The field of this invention is calipers for detecting internal surface variations in pipes.
In U.S. Pat. No. 2,933,819, a pipe caliper is disclosed wherein a strain gauge is located on each feeler and the assembly is interconnected in such a manner that separate removal and replacement of individual feelers in the field would disturb the electrical system and therefore would be difficult, if not impossible, thereby usually necessitating the delay and expense of shop repair.